This invention relates to a temperature compensation system for a matrix type liquid crystal display which has a liquid crystal layer in the cross points between the longitudinal drive electrodes and the lateral drive electrodes.
Nowadays, a liquid crystal display is used broadly as the display for an electronic timepiece.
It is used generally since it has a low current consumption, a low voltage and has a long lifetime with a small sized battery.
There is a static driving system for a liquid crystal and a dynamic driving system for the above mentioned liquid crystal display.
In the operation of the static driving system, the operating temperature range of the display is broad, namely about 0.degree. C. to 50.degree. C. at which the display operates with stability so that it obtains a practical and sufficient display effect.
However, the dynamic driving system using a time sharing method is adopted instead of the static driving system since the circuit construction in the static driving system is complicated and has a big size because of the increase of display information and of the variety of display characters.
It is disadvantageous that the dynamic driving system is narrower than the static driving system in the operating temperature range, since it generates the cross-talk phenomenon at 40.degree. C. it exhibits a poor display at the non-selecting portion, it has a poor contrast at below 10.degree. C., and it generates a incomplete display when there is a delay in the response time.
FIG. 1 shows the characteristic-variation of the effective voltage with respect to the temperature of the conventional dynamic driving system. Von is the effective voltage applied to the selecting segment and Voff is the effective voltage applied to the non-selecting segment.
In FIG. 1. cross-talk is produced at about 35.degree. C. because Voff is greater than V.sub.th, which is the threshold voltage of the liquid crystal.
On the other hand, incompleteness of contrast is initiated at a low temperature of about 15.degree. C. because Von is greater than Vsat which is the saturation voltage of the liquid crystal.
Conventionally, there is the change-over system which changes the frequency of the driving pulse applied to a liquid crystal and the voltage thereof corresponding to signals which are generated by a thermistor which detects the ambient temperature-variation of the display, in order to compensate for the temperature-variation.
However, it is disadvantageous that this control system does not control the change of the electro-light characteristic depending upon aging changes and is subjected to limitations in the cost and design as a result of the addition of the element such as a thermistor in a limited space such as an electronic watch space.